MATLAB writing csv with mixed alphanumeric strings, scalar arrays, nans - matlab

Question

Ok, coming from Python and never having used MATLAB before, it seems like it is unnecessarily hard to write data to a csv using MATLAB...
So my data looks like this:
col1 A2A B2 CC3 D5
asd189 123 33 71119 18291
as33d 1311 31 NaN 1011
asd189 NaN 44 79 191
It has N header columns that are made of alphanumeric strings.
It has a leftmost column of length M which is made of alphanumeric strings.
It has an (M-1) x (N-1) array of NUMERIC data, with possible NaNs.
Can you please provide code to write this to a csv? I cannot use the xlswrite function because I'm on a cluster without Excel installed. Really just want to get on with the actual data analysis. Thanks

Answer 1

You can only write matrices (not cell arrays) directly using csvwrite, and as you say you need Excel installed for xlswrite, so that leaves you with low level operations. You can see a walkthrough for writing to text files here, and code for your example below:
% Initialise example cell array
M = {'col1', 'A2A', 'B2', 'CC3', 'D5'
'asd189', 123, 33, 71119, 18291
'as33d', 1311, 31, NaN, 1011
'asd189', NaN, 44, 79, 191};
% Open a file for writing to (doesn't have to already exist, can specify full directory)
fID = fopen('test.csv','w');
% Write header line, formatted as strings with comma delimiter. Note \r\n for new line
fprintf(fID, [repmat('%s, ', 1, size(M,2)-1),'%s\r\n'], M{1,:});
% Loop through other rows
for row = 2:size(M,1)
% Write each line of cell array, with first column formatted as string
% and other columns formatted as floats
fprintf(fID, ['%s, ', repmat('%f, ', 1, size(M,2)-2),'%f\r\n'], M{row,:});
end
% Close file after writing
fclose(fID);
Result:

Answer 2

Use writetable. It makes writing to CSV (or to an Excel file, or to other text-delimited file formats) much easier than using csvwrite, or xlswrite, or low-level commands such as fprintf.
>> t = table({'asd189';'as33d';'asd189'},[123;1311;NaN],[33;31;44],[71119;NaN;79],[18291;1011;191]);
>> t.Properties.VariableNames = {'col1','A2A','B2','CC3','D5'}
t =
col1 A2A B2 CC3 D5
________ ____ __ _____ _____
'asd189' 123 33 71119 18291
'as33d' 1311 31 NaN 1011
'asd189' NaN 44 79 191
>> writetable(t,'myfile.csv')
If your data is currently not stored as a table (maybe it's in an array or cell array), it's pretty easy to convert to a table using utility functions such as array2table or cell2table. You will only pay a small time penalty for doing this.
PS - you don't need Excel to be installed in order to write to an Excel file. You may not be able to read them afterwards, but MATLAB can still write them. But it sounds like you'd prefer .csv anyway.